Fix fast-path plan creation to be mindful of the finishing's offset

Author: ggevay

src/adapter/src/coord/peek.rs

@@ -465,13 +465,16 @@ pub fn create_fast_path_plan<T: Timestamp>(
             {
                 if let Some(finishing) = finishing {
                     if group_key.is_empty() && *order_key == finishing.order_by && *offset == 0 {
-                        // The following is roughly `limit >= finishing.limit`, but with Options.
+                        // The following is roughly `limit >= finishing.limit + finishing.offset`,
+                        // but with Options.
                         let finishing_limits_at_least_as_topk = match (limit, finishing.limit) {
                             (None, _) => true,
                             (Some(..), None) => false,
                             (Some(topk_limit), Some(finishing_limit)) => {
                                 if let Some(l) = topk_limit.as_literal_int64() {
-                                    l >= *finishing_limit
+                                    i128::cast_from(l)
+                                        >= i128::cast_from(*finishing_limit)
+                                            + i128::cast_from(finishing.offset)
                                 } else {
                                     false
                                 }

test/sqllogictest/topk.slt

@@ -183,3 +183,86 @@ Source materialize.public.cities
 Target cluster: quickstart
 
 EOF
+
+# Regression test for https://github.com/MaterializeInc/database-issues/issues/11292
+# i.e., that when `create_fast_path_plan` jumps through a TopK, it correctly takes into account the finishing's offset.
+statement ok
+CREATE TABLE t (x int);
+
+statement ok
+INSERT INTO t VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11),(12),(13),(14),(15),(16),(17),(18),(19),(20);
+
+query I
+SELECT * FROM (SELECT * FROM t LIMIT 12) LIMIT 10 OFFSET 5;
+----
+6
+7
+8
+9
+10
+11
+12
+
+query I
+SELECT * FROM (SELECT * FROM t ORDER BY x LIMIT 12) ORDER BY x LIMIT 10 OFFSET 5;
+----
+6
+7
+8
+9
+10
+11
+12
+
+query I
+SELECT * FROM (SELECT * FROM t LIMIT 15) LIMIT 10 OFFSET 5;
+----
+6
+7
+8
+9
+10
+11
+12
+13
+14
+15
+
+statement ok
+CREATE DEFAULT INDEX ON t;
+
+query I
+SELECT * FROM (SELECT * FROM t LIMIT 12) LIMIT 10 OFFSET 5;
+----
+6
+7
+8
+9
+10
+11
+12
+
+query I
+SELECT * FROM (SELECT * FROM t ORDER BY x LIMIT 12) ORDER BY x LIMIT 10 OFFSET 5;
+----
+6
+7
+8
+9
+10
+11
+12
+
+query I
+SELECT * FROM (SELECT * FROM t LIMIT 15) LIMIT 10 OFFSET 5;
+----
+6
+7
+8
+9
+10
+11
+12
+13
+14
+15